A conventional cleaner is shown in FIG. 1, a bottom of a main body 1 of the cleaner is flat and fixed, and is only about 0.3-0.5 centimeters high from the ground. When the ground is flat and has no obstacles, the cleaner can move normally. Once the main body 1 of the cleaner encounters a bigger obstacle such as a pencil or small nail, the main body 1 of the cleaner will be blocked and cannot move.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.